The present invention relates to a safety device for pneumatic actuators.
More specifically, the present invention relates to a safety device for pneumatic actuators, specifically designed for preventing the actuator pinion from being violently ejected, under the axial pushing force exerted on the actuator piston by the pressure inside the actuator body.
As known, an actuator pinion is conventionally formed by a single cylindric piece passing through the tubular body of the actuator, perpendicularly to the axis thereof.
Said pinion is provided with different diameters at different portions of the length thereof, and the two cylindric portions of the pinion, communicating with the outside of the actuator body, are sealed with respect to said body by two gaskets, for example two O-rings.
The diameter difference at the end portions of said pinion causes said pinion to be urged by the pressure inside the pneumatic actuator body, in a different manner depending on the cross-section on which said pressure is applied.
This fact generates a pushing force in the direction of the larger cross-section of said pinion, tending to cause the pinion to be ejected from the actuator body.
This pushing or urging force is conventionally counter-biassed in different manners, for example by using a resilient metal ring element, of the type of the so-called Seeger ring, applied to the pinion less diameter projecting portion, outside of the pneumatic actuator body.
However, it would be advantageous to provide a further safety device aiding the above metal resilient ring element and adapted to provide a great operation safety, for example if the mentioned ring element is erroneously applied or fails.
In fact, if the actuator pinion is not properly restrained, as pressurized air is supplied to the inside of the actuator body, then said pinion can be projected with such a force susceptible to seriously damage persons and things which are present within a distance range of several meters from the actuator.
This would be particularly dangerous if the actuator pinion has a large size, considering that the weight of such a pinion can be of the order of some tens of kilograms.
In order to safely prevent the pinion from operating as an impacting projectile, specifically designed safety actuators have been provided, which, however, have a very high cost.
Moreover, in said safety actuators, because of their rather complex construction, the pinion can be assembled with great difficulties and the angular position of said pinion can be hardly changed, and, consequently, said pinion must be frequently disassembled and assembled again in order to modify its position with respect to the actuator body, said disassembling and assembling steps being performed either in the actuator making shop or directly on the system on which the actuator is installed.